Bioelectrical impedance analysis as a means of estimating total body waterin grey seals

Estimates of total body water (TBW) play an important role in studies of bo dy composition and energetics in mammals. We evaluated bioelectrical impeda nce analysis (BIA) as a means of rapidly and inexpensively estimating TBW i n 38 grey seals (Halichoerus grypus). Twenty-two males and 16 females, repr esenting the range of body sizes in the population, were studied at Sable I sland, Nova Scotia. Seals were chemically immobilized with Telazol during B IA measurement. TBW was determined by dilution of tritiated water. The mean difference in duplicate BIA. measurements did not differ significantly fro m zero. BIA-measured resistance accounted for 83% of the variation in TBW o ver a range of body masses from 38.5 to 294 kg. Bioelectrical conductor vol ume (length(2)/resistance) accounted for 97% of the variation in TBW Averag e error in predicting TBW was +0.10% for a validation set of nine animals, but errors in predicting TBW of individual seals were up to 25%. Our result s indicate that BIA measurements can be a valuable adjunct to the use of is otope dilution for estimating TBW in chemically immobilized grey seals; how ever, individual estimates may be associated with varying degrees of error.